Measurement Of Atmospheric Density Based On UV Laser Rayleigh Scattering

Density is one of the most important parameters of the flow. It plays an important role in t he r esearch a reas o f aviation a nd s pace, military m eteorology, bur ning, atmospheric physics, etc. The spatial resolution of traditional flow measuring methods is low, and their ability of measuring complicated 3D density field is limited, so the distribution of flow density field can not be well showed. With the development of laser and other technology, a new flow detection technique called laser and molecular flow detection t echnique is generated. I n t his paper, w e use Rayleigh scat tering method and successfully measure the density of the atmosphere.The main work of the paper can be divided into three parts as below:The f irst p art m ainly analyzes an d co mpares t he principles, ad vantages an d disadvantages, f itting situations of s ome ki nds of l aser f low de tection t echnique. Through that, we obtain the result that for the measuring of flow density, using the method of 266nm UV Rayleigh scattering can get good outcome.In the second part, we first introduce the principle of measuring the flow density using Rayleigh s cattering method. Then we de sign t he structural d iagram of t he system, an d d iscuss the so lutions o f temporal re solution, spatial re solution of t he system, U V l aser, synchronization and receiving system. F inally, w e d iscuss t he impact of system parameters and structure on the measuring result.In the third part, we discuss the experiment of flow density measurement using UV Rayleigh scattering method. First, we introduce the principle of the experiment of Rayleigh scattering. And then we introduce the experiment of 266nm UV laser. We use Nd:YAG laser with xenon lamp pumping to generate 1064nm pulse laser. The laser passes through KTP crystal and BBO crystal to make its frequency doubled. Finally, we successfully get the output UV pulse laser with the energy of 6.1mJ, pulse width of less than 5ns, peak power of more than 1.2MW. At last, we introduce the experiment of measuring the density of nitrogen in the air cell. After that, we get the relationship between the intensity of the scattering light and the air pressure. With some suitable calibration methods, we can get the density of the gas.